Spring源码学习--BeanPostProcessor接口

文章来源:

http://www.cnblogs.com/sishang/p/6576665.html

public interface BeanPostProcessor {

    /**
     * 实例化、依赖注入完毕，在调用显示的初始化之前完成一些定制的初始化任务  
     */
    Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException;

    /**
     * 实例化、依赖注入、初始化完毕时执行  
     */
    Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException;

}

由API可以看出:

后置处理器的postProcessorBeforeInitailization方法是在bean实例化，依赖注入之后及自定义初始化方法(例如：配置文件中bean标签添加init-method属性指定Java类中初始化方法、@PostConstruct注解指定初始化方法，Java类实现InitailztingBean接口)之前调用
后置处理器的postProcessorAfterInitailization方法是在bean实例化、依赖注入及自定义初始化方法之后调用

注意：

BeanFactory和ApplicationContext两个容器对待bean的后置处理器稍微有些不同。ApplicationContext容器会自动检测Spring配置文件中那些bean所对应的Java类实现了BeanPostProcessor
接口，并自动把它们注册为后置处理器。在创建bean过程中调用它们，所以部署一个后置处理器跟普通的bean没有什么太大区别。
BeanFactory容器注册bean后置处理器时必须通过代码显示的注册，在IoC容器继承体系中的ConfigurableBeanFactory接口中定义了注册方法

/**  
 * Add a new BeanPostProcessor that will get applied to beans created  
 * by this factory. To be invoked during factory configuration.  
 * <p>Note: Post-processors submitted here will be applied in the order of  
 * registration; any ordering semantics expressed through implementing the  
 * {@link org.springframework.core.Ordered} interface will be ignored. Note  
 * that autodetected post-processors (e.g. as beans in an ApplicationContext)  
 * will always be applied after programmatically registered ones.  
 * @param beanPostProcessor the post-processor to register  
 */    
void addBeanPostProcessor(BeanPostProcessor beanPostProcessor);

Spring如何调用多个BeanPostProcessor实现类

我们可以在Spring配置文件中添加多个BeanPostProcessor(后置处理器)接口实现类，在默认情况下Spring容器会根据后置处理器的定义顺序来依次调用。

Spring配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
    <bean id="narCodeService" class="com.test.service.impl.NarCodeServiceImpl">
    </bean>
    <bean id="postProcessor" class="com.test.spring.PostProcessor"/>
    <bean id="postProcessorB" class="com.test.spring.PostProcessorB"/>
</beans>

BeanPostProcessor实现类：

package com.test.spring;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
/**
 * bean后置处理器
 * @author zss
 *
 */
public class PostProcessor implements BeanPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器处理bean=【"+beanName+"】开始");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器处理bean=【"+beanName+"】完毕!");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }
}

package com.test.spring;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

public class PostProcessorB implements BeanPostProcessor {

    @Override
    public Object postProcessBeforeInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器开始调用了");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器调用结束了");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }
}

测试:

package com.test.spring;

import org.junit.Before;
import org.junit.Test;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class T {
    AbstractApplicationContext applicationcontext=null;
    @Before
    public void before() {
        System.out.println("》》》Spring ApplicationContext容器开始初始化了......");
        applicationcontext= new ClassPathXmlApplicationContext(new String[]{"test1-service.xml"});
        System.out.println("》》》Spring ApplicationContext容器初始化完毕了......");
    }
    @Test
    public void  test() {
        applicationcontext.registerShutdownHook();   
    }
}

测试结果:

》》》Spring ApplicationContext容器开始初始化了......
2017-03-19 10:50:29  INFO:ClassPathXmlApplicationContext-Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@18c92ff9: startup date [Sun Mar 19 10:50:29 CST 2017]; root of context hierarchy
2017-03-19 10:50:29  INFO:XmlBeanDefinitionReader-Loading XML bean definitions from class path resource [test1-service.xml]
后置处理器处理bean=【narCodeService】开始
后置处理器开始调用了
后置处理器处理bean=【narCodeService】完毕!
后置处理器调用结束了
》》》Spring ApplicationContext容器初始化完毕了......
2017-03-19 10:50:34  INFO:ClassPathXmlApplicationContext-Closing org.springframework.context.support.ClassPathXmlApplicationContext@18c92ff9: startup date [Sun Mar 19 10:50:29 CST 2017]; root of context hierarchy

在Spring机制中可以指定后置处理器调用顺序，通过让BeanPostProcessor接口实现类实现Ordered接口getOrder方法，该方法返回一整数，默认值为 0，优先级最高，值越大优先级越低

package com.test.spring;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.core.Ordered;
/**
 * bean后置处理器
 * @author zss
 *
 */
public class PostProcessor implements BeanPostProcessor,Ordered{

    @Override
    public Object postProcessBeforeInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器处理bean=【"+beanName+"】开始");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器处理bean=【"+beanName+"】完毕!");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }

    @Override
    public int getOrder() {
        return 1;
    }
}

package com.test.spring;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.core.Ordered;

public class PostProcessorB implements BeanPostProcessor,Ordered {

    @Override
    public Object postProcessBeforeInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器开始调用了");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean,
            String beanName) throws BeansException {
        System.out.println("后置处理器调用结束了");
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return bean;
    }

    @Override
    public int getOrder() {
        return 0;
    }
}

测试结果:

》》》Spring ApplicationContext容器开始初始化了......
2017-03-19 11:04:10  INFO:ClassPathXmlApplicationContext-Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@18c92ff9: startup date [Sun Mar 19 11:04:10 CST 2017]; root of context hierarchy
2017-03-19 11:04:10  INFO:XmlBeanDefinitionReader-Loading XML bean definitions from class path resource [test1-service.xml]
后置处理器开始调用了
后置处理器处理bean=【narCodeService】开始
后置处理器调用结束了
后置处理器处理bean=【narCodeService】完毕!
》》》Spring ApplicationContext容器初始化完毕了......
2017-03-19 11:04:14  INFO:ClassPathXmlApplicationContext-Closing org.springframework.context.support.ClassPathXmlApplicationContext@18c92ff9: startup date [Sun Mar 19 11:04:10 CST 2017]; root of context hierarchy

Spring源码学习--BeanPostProcessor接口

文章来源:

Spring如何调用多个BeanPostProcessor实现类

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